Synthesis and current–voltage characterization of tin dioxide varistors

Abstract

An overview of the steady state electrical properties of tin dioxide varistors is presented. The varistors are manufactured in two ways: (1) a ceramic route by mixing and compaction of tin dioxide powder with various dopants and (2) a sol-gel method, where dopants are dispersed in their aqueous solutions. For a quantitative agreement with the experimental data, the electronic defect states in the bulk of the tin dioxide grains and at the grain boundary interfaces are studied. Scanning electron microscope and x-ray diffraction are employed to study the morphological and structural aspects of tin dioxide varistors. The effect of various sintering temperatures on their nonohmic or nonlinear characteristics was also investigated. The varistors prepared by the sol-gel method showed high nonlinearity, high density, and high threshold voltage properties than the ones produced by the ceramic route. This is probably due to a finer grain structure and a better densification of dopants along the grain boundaries.

A comparative study between the mixed-oxide and high-energy milling planetary method on electrical and microstructural properties for a SnO2-based ceramic system

“…The intermediate nonlinear region is considered as the heart of the varistor. In this region the device conducts an increasingly large amount of electric current for a small increase in voltage (Kale et al, 1999), and therefore it becomes able to divert a transient so that pulse energy will be dissipated elsewhere. The transition value between the linear and nonlinear regions is known as the breakdown voltage V B , or breakdown electric field E B , and defines the varistor operation range.…”

“…Finally, in the last region (the high-current region) characterized by grain control, the current-voltage characteristics are linear again as occurs in the first region. Since zinc oxide [ZnO] material was introduced by Matsuoka (1971), it has been the most extensively studied material and used as the base for ceramic systems, consequently it became the most important ceramic for commercial production of varistors (Clarke, 1999;Peiteado, 2005;Wang et al, 2003;Kale et al, 1999;Matsuoka, 1971). Due to the need of attaining varistors with better properties, there has recently been a great interest in other ceramic materials, e.g.…”